1. Field of the Invention
The present invention relates to an exhaust pump that is used, as gas evacuation means or the like, in a process chamber of a semiconductor manufacturing apparatus, a flat panel display manufacturing apparatus or a solar panel manufacturing apparatus, and in other sealed chamber. More particularly, the invention relates to an exhaust pump provided with connecting opening portions that can be deburred easily and that are suitable for enhancing gas evacuation performance.
2. Description of the Related Art
One known method for enhancing the evacuation performance of an exhaust pump of a type where gas is evacuated by using a thread groove, but without modifying the overall size of the pump, is, for instance, the method disclosed in Japanese Unexamined Utility Model Application Laid-open No. H5-38389.
In this method, as illustrated in FIG. 1 of Japanese Unexamined Utility Model Application Laid-open No. H5-38389, thread grooves (30, 31) are provided at the outer periphery and the inner periphery of a cylindrical rotating member (4a). As a result, a helical outer thread groove exhaust passage becomes formed between the cylindrical rotating member (4a) and an outer cylindrical fixed member (33) that surrounds the outer periphery of the cylindrical rotating member (4a), and a helical inner thread groove exhaust passage becomes formed between the cylindrical rotating member (4a) and an inner cylindrical fixed member (7) that surrounds the inner periphery of the cylindrical rotating member (4a), such that gas molecules are evacuated in parallel along these inner and outer thread groove exhaust passages (parallel-flow evacuation scheme).
In order to lead the gas molecules to the inner thread groove exhaust passage in the exhaust pump that relies on the above parallel-flow evacuation scheme, a configuration is resorted to wherein connecting opening portions (4b) are opened in the cylindrical rotating member (4a) (FIG. 1 in Japanese Unexamined Utility Model Application Laid-open No. H5-38389). Rotor blades (5) exist above the upstream end of the connecting opening portions (4b), and hence the connecting opening portions (4b), if any, are formed through drilling by inserting a long tool, from the inward side of the cylindrical rotating member (4a).
In a method where the connecting opening portions (4b) are formed through such drilling, however, burr forms at the upstream end of the connecting opening portions (4b). If the abovementioned rotor blades (5) exist on the upstream end side of the connecting opening portions (4b), therefore, the rotor blades (5) hamper the deburring operation, and it is no longer possible to remove burr in a simple manner.
The exhaust pump that utilizes the abovementioned parallel-flow evacuation scheme has enhanced evacuation performance. However, recent years have witnessed an increase in the size of the sealed chambers, and in the amount of gases, such as reactive gases and the like, that are used in these chambers, as dictated by the increase in size of the semiconductors, flat panels, solar panels and the like that are produced in such sealed chambers. Accordingly, yet better evacuation performance is required from exhaust pumps as means for evacuating such gases.
The reference numerals in brackets in the explanation above denote reference numerals used in Japanese Unexamined Utility Model Application Laid-open No. H5-38389.